Endoprostheses for replacement of an intervertebral disk of the cervical spine are known (FR-A-2 718 635, EP-B-699 426) which consist of two cover plates and a joint core. The cover plates, which are arranged approximately parallel on both sides of the core, have connection surfaces which are intended for connection to the adjacent vertebral bodies. The cranial vertebral body cover plates, which are to be connected to a lower prosthesis cover plate, have a roughly rectangular shape. They are approximately flat and are delimited at the sides by edge serrations. The caudal vertebral body cover plates have extensive edge serrations at the ventral edge. These have to be removed before the prosthesis is fitted. It is also expedient for the vertebral body surfaces which are intended to bear on the prosthesis to be worked in order to adapt them to the connection surfaces of the prosthesis.
The connection surfaces of the known prostheses mentioned are circularly delimited. Since the end plates of the vertebral bodies have approximately the shape of a rectangle whose width is substantially greater than its dimension in the anteroposterior direction, they do not exploit the size of the naturally occurring surfaces for force transmission. Accordingly, between the connection surfaces of the prosthesis and the bearing surfaces on the vertebral bodies, greater forces occur than would be the case if the surfaces were better utilized. In the case of intervertebral disk endoprostheses intended for the lumbar spine, the best utilization of space is achieved by using an oval prosthesis contour (WO 0 101 893, EP-B-471 821, EP-A-747 025) or a kidney-shaped configuration (EP-A-747 025), because the cover plates of the vertebral bodies have an oval to kidney-shaped configuration. Rectangular prosthesis shapes are also known (U.S. Pat. No. 5,425,773).